''Helicobasidium'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

in the

subdivision Subdivision may refer to: Arts and entertainment * Subdivision (metre), in music * ''Subdivision'' (film), 2009 * "Subdivision", an episode of ''Prison Break'' (season 2) * ''Subdivisions'' (EP), by Sinch, 2005 * "Subdivisions" (song), by Rush ...

Pucciniomycotina Pucciniomycotina is a subdivision of fungus within the division Basidiomycota. The subdivision contains 10 classes, 21 orders, and 38 families. Over 8400 species of Pucciniomycotina have been described - more than 8% of all described fungi. T ...

Basidiocarps In fungi, a basidiocarp, basidiome, or basidioma () is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do no ...

(fruit bodies) are

corticioid The corticioid fungi are a group of fungi in the Basidiomycota typically having effused, smooth basidiocarps (fruit bodies) that are formed on the undersides of dead tree trunks or branches. They are sometimes colloquially called crust fungi or pa ...

(patch-forming) and are typically violet to purple. Microscopically they have auricularioid (laterally septate)

basidia A basidium (: basidia) is a microscopic spore-producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi. The presence of basidia is one of the main characteristic features of the group. These bodies are also ...

. Asexual

anamorphs In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an asex ...

, formerly referred to the genus ''Thanatophytum'', produce

sclerotia A sclerotium (; : sclerotia () is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot, sclerotia become detached and remain dormant u ...

Conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

-bearing anamorphs are parasitic on

rust fungi Rusts are fungal plant pathogens of the order Pucciniales (previously known as Uredinales) causing plant fungal diseases. An estimated 168 rust genera and approximately 7,000 species, more than half of which belong to the genus ''Puccinia'', are ...

and are currently still referred to the genus '' Tuberculina''. Species are opportunistic

plant pathogens Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...

, causing violet root rot of root crops and other plants of economic importance. The name "violet root rot" refers to the dark purple colour of the

mycelial Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fou ...

mats formed on the infected plants, usually at or below the

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

line. It can cause total rot and structural failure of roots and subterranean storage organs. Impact of violet root rot on crop loss is often due to stunting of above ground plant growth and decreased vigour, and in extreme cases, whole plant death. It does not directly infect above ground organs. Violet root rot can also damage or cause the death of subterranean storage organs such as potato

tuber Tubers are a type of enlarged structure that plants use as storage organs for nutrients, derived from stems or roots. Tubers help plants perennate (survive winter or dry months), provide energy and nutrients, and are a means of asexual reproduc ...

s or carrots.

Taxonomy

History

The genus was first described in 1885 by French

mycologist Mycology is the branch of biology concerned with the study of fungi, including their taxonomy, genetics, biochemical properties, and use by humans. Fungi can be a source of tinder, food, traditional medicine, as well as entheogens, poison, and ...

Narcisse Théophile Patouillard Narcisse Théophile Patouillard (2 July 1854 – 30 March 1926) was a French pharmacist and mycologist. He was born in Macornay, a town in the department of Jura (department), Jura. He studied in Besançon, then furthered his education at the ...

to accommodate a purple, incrusting, terrestrial fungus with helicoid (spiralled), auricularioid (laterally septate) basidia which he considered distinct. Subsequent authors added additional species with similarly helicoid basidia, though not all had similarly coloured fruit bodies. ''

Rhizoctonia ''Rhizoctonia'' is a genus of fungi in the family Ceratobasidiaceae. Species form thin, effused, corticioid basidiocarps (fruit bodies), but are most frequently found in their sterile, anamorph state. ''Rhizoctonia'' species are saprotrophic, ...

'' was introduced in 1815 by French mycologist

Augustin Pyramus de Candolle Augustin Pyramus (or Pyrame) de Candolle (, , ; 4 February 17789 September 1841) was a Swiss people, Swiss botany, botanist. René Louiche Desfontaines launched de Candolle's botanical career by recommending him at a herbarium. Within a couple ...

for plant pathogenic fungi that produce hyphae and

. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''Rhizoctonia crocorum'', was purple and incrusting and later shown to be an

anamorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an ase ...

ic form of ''Helicobasidium'' in a series of observations and innoculation trials conducted in part by

Kew Kew () is a district in the London Borough of Richmond upon Thames. Its population at the 2011 census was 11,436. Kew is the location of the Royal Botanic Gardens ("Kew Gardens"), now a World Heritage Site, which includes Kew Palace. Kew is ...

mycologist Elsie Wakefield. ''Rhizoctonia'' had, however, become an artificial

form genus Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of sc ...

containing a mix of unrelated species. As part of a move towards a more natural classification, the type species was transferred to ''

Rhizoctonia solani ''Rhizoctonia solani'' is a species of fungus in the order Cantharellales. Basidiocarps (fruit bodies) are thin, effused, and web-like, but the fungus is more typically encountered in its anamorphic state, as hyphae and sclerotia. The name ' ...

'' (to preserve the most commonly used name) and ''R. crocorum'' transferred to its earliest synonym ''Thanatophytum crocorum''. ''Tuberculina'' was introduced in 1880 by Italian mycologist

Pier Andrea Saccardo Pier Andrea Saccardo (23 April 1845 in Treviso, Province of Treviso, Treviso – 12 February 1920 in Padua, Italy, Padua) was an Italian botany, botanist and mycology, mycologist. His multi-volume ''Sylloge Fungorum'' was one of the first attempt ...

for

conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

-bearing fungi parasitizing rust fungi.

Current status

Molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...

research, based on

cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...

analysis of

DNA sequences A nucleic acid sequence is a succession of bases within the nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. This succession is denoted by a series of a set of five different letters that indicate the order of the ...

, has shown that all of three states - basidial, sclerotial, and conidial - are forms of the same genus of fungi. Following changes to the

International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN or ICNafp) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all tho ...

, the practice of giving different names to

teleomorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an ase ...

and

forms of the same fungus was discontinued, meaning that ''Thanatophytum'' and ''Tuberculina'' became synonyms of the more commonly used name ''Helicobasidium''. ''Helicobasidium''

sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...

appears to be confined to a group of purple plant and rust pathogens whose taxonomy is currently unclear. Initial DNA sequencing has revealed at least seven species within the genus, but assigning names to them "demands a revision of the species concept within the group" which is yet to be undertaken. As a result, species of ''Tuberculina'' are not yet integrated within the genus ''Helicobasidium''. A few additional species described in ''Helicobasidium''

sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

, including '' Helicobasidium corticioides'', are not closely related to the type species and are of uncertain disposition within the Pucciniomycotina.

Violet root rot: hosts and symptoms

The most indicative sign of violet root rot is the presence of dark fungal mats on the affected plant’s roots and stem near the soil line, and the presence of mycelium on the soil. ''Helicobasidium'' species are opportunistic parasites of subterranean plant organs. Symptoms of infection include foliage

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

, premature

abscission Abscission () is the shedding of various parts of an organism, such as a plant dropping a leaf, fruit, flower, or seed. In zoology, abscission is the intentional shedding of a body part, such as the shedding of a claw, husk, or the autotomy of a ...

, wilting, and severe reduction of root mass. Infected soil may be identified by the conspicuous nature of the webbed mycelium, which transitions from white to dark violet over the growing season. Violet root rot can infect a wide range of commercial crops, including

apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

(''Malus domestica),''

mulberry ''Morus'', a genus of flowering plants in the family Moraceae, consists of 19 species of deciduous trees commonly known as mulberries, growing wild and under cultivation in many temperate world regions. Generally, the genus has 64 subordinat ...

(''Morus spp)'',

grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began approximately 8,0 ...

(''Vitus spp)'',

potato The potato () is a starchy tuberous vegetable native to the Americas that is consumed as a staple food in many parts of the world. Potatoes are underground stem tubers of the plant ''Solanum tuberosum'', a perennial in the nightshade famil ...

(''Solanum tuberosum)'',

plum A plum is a fruit of some species in Prunus subg. Prunus, ''Prunus'' subg. ''Prunus'.'' Dried plums are often called prunes, though in the United States they may be labeled as 'dried plums', especially during the 21st century. Plums are ...

(''Prunus spp)'', tea,

beets The beetroot (British English) or beet (North American English) is the taproot portion of a ''Beta vulgaris'' subsp. ''vulgaris'' plant in the Conditiva Group. The plant is a root vegetable also known as the table beet, garden beet, dinner beet ...

soy The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source of f ...

, and

cotton Cotton (), first recorded in ancient India, is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure ...

. It can also infect many more host plants and is not selective.

Violet root rot: disease cycle

''Helicobasidium'' species are

soil borne pathogen A soil borne pathogen is a disease-causing agent which lives both in soil and in a plant host, and which will tend to infect undiseased plants which are grown in that soil. Common soil borne pathogens include ''Fusarium'', '' Pythium'', '' Rhizocto ...

s. The pathogen overwinters both as

and via mycelium;

basidiospore A basidiospore is a reproductive spore produced by basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid Ploidy () is the number of complete sets of chromos ...

s are not known to play a significant role in the disease cycle. Autumn sclerotia production is initiated by nutrient deficits; in the early growing season when the host and moisture are present again the sclerotia will resume growth and infection of the host. Sclerotia are dispersed through movement in

irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

or rain water, particularly of note where flood irrigation is used. ''Helicobasidium'' species will grow as an independent, whitish mycelium for the first part of the growing season, gradually darkening from pink to a dark violet brown as infection progresses mid-season. Infection occurs via an external infection cushion from which penetrating

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

e infest the

lamellae Lamella (: lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology), a papery rib beneath a mushroom cap * Lamella (botany) * Lamella (surface anatomy), a plate-like structure in an animal * Lame ...

of root tissues, where they cause damage. The dark pigment found in ''Helicobasidium'' species is helicobasidin and can be toxic to some plants and microorganisms.

Violet root rot: management

This disease is mostly controlled through cultural means. Resistant varieties can be an effective method to stifle disease progress, as well as early maturing annual crops which avoid infection altogether. Harvesting before the fungus has a chance to infect the crop is also a viable option. As

cereal A cereal is a grass cultivated for its edible grain. Cereals are the world's largest crops, and are therefore staple foods. They include rice, wheat, rye, oats, barley, millet, and maize ( Corn). Edible grains from other plant families, ...

grains are not affected, long

rotations Rotation or rotational/rotary motion is the circular movement of an object around a central line, known as an ''axis of rotation''. A plane figure can rotate in either a clockwise or counterclockwise sense around a perpendicular axis intersec ...

with grains can reduce incidence. The fungus requires ample moisture, warm soil temperatures (20-30 °C) and low pH to thrive, drip irrigation and regular

lime Lime most commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Bo ...

applications can serve to reduce the fungal presence.

References

{{Taxonbar, from=Q5705041 Basidiomycota genera Pucciniomycotina Taxa named by Narcisse Théophile Patouillard Taxa described in 1885 Fungal plant pathogens and diseases